In aerospace, defense, energy production, and energetic materials applications it is often of interest to measure the precise location of energetic penetration or rupture of a surface or volume of interest. It is also of interest to characterize the impact if possible. In these and other applications it is often of interest to measure a precise location of contact between impacting or colliding bodies.
This invention has application to any field that requires local damage site characterization from energetic impacts, fire or high-temperature failure modes, explosive devices, munitions development, structure blast survivability studies, energetic propellant characterization, or surface damage due to extreme environments, such as occur in a detonation of an explosive or with space vehicles re-entering the Earth's atmosphere. Other applications include aircraft and building fire detection, rocket booster failure detection, and combat vehicle damage detection, location, and notification. Satellite and space station damage due to meteorite impacts is another application. For lower energetic encounters, an adaptation employing different low energy sensing modalities can enable non-destructive contact sensing as opposed to impact or penetration sensing.
U.S. Government agencies, such as the Missile Defense Agency (MDA), have interests in such technology in the field of missile defense where it is desired to destroy incoming enemy missiles. It is important to know the impact point or the multiple impact points that may occur in an interceptor engagement as well as the progression of the resulting damage through the particular target of interest. Tactical weapon lethality testing by the U.S. Army, Air Force, and Navy also requires knowledge of the hit-point on a particular target such as an armored vehicle, aircraft, ship, submarine, or bunker. Additionally, the National Aeronautics and Space Administration (NASA) has interest in damage assessment due to high-velocity impacts of debris and meteorites on space vehicles, as well as detection and location of potential burn-through and catastrophic failure of rocket boosters.
There are a number of existing hit-point electrical and optical sensor systems, which can either detect or estimate the location of an energetic penetration of surfaces. Optical systems include conventional optical grids and similar approaches such as the Break Detection System (U.S. Pat. No. 5,013,908 to Chang), which uses a grid of fiber optic cables as a detection system. It is important to note that this system is an “active” sensing system, requiring injection of an optical and modulated signal to continuously power an unbroken grid, so as to sense location of a broken optical conductor upon breakage from a penetration. A first drawback of using electrical detection techniques as above is that they are more complex since optical signals must be developed by electrical or RF power sources for each sensing line. This adds complexity and expense to the system. A second drawback is that the added complexity of these same electrical or RF power sources reduces the reliability of the system since if the source is inoperable, so too is the at least that line of the system. A third drawback of such systems is that during energetic events, electronics of the system often are disrupted by electromagnetic interference (EMI) that can cause corruption of the data. A further drawback is that, at least in the Chang reference, only location is detected, with no reference to timing. Yet another drawback is that no detection of subsequent “hits” is possible in a broken cable segment.
A number of optical techniques have also been developed over the years to try to address at least some of these issues. Johns Hopkins University Applied Physics Laboratory (JHU APL) has developed several optical techniques including the Light-Speed Hitpoint Sensor (LSHS). Although this system is also a passive system, it is more complex and incapable of determining multiple hit-point locations once its single fiber is severed because of the architecture employed and its time of flight measurement can also be confused by multiple impact detections.
Another example of an optical system developed by JHU APL is the Blast Initiation Detector (BID). The BID detects the time of a collision by viewing the exterior of the surface. The BID is a high-speed instrument that detects rapid onset optical events. It has a wide field-of-view and uses high-temperature optical fibers that maintain their field-of-view and optical throughput during rapid heating that occurs during reentry into the earth's atmosphere.
JHU APL also developed the Planar Optical Penetration Sensors (POPS). The POPS sensor includes a sandwich of a transparent layer within two reflective layers, which in turn are within two opaque layers. An optical sensor structure includes a set of sensors positioned in respective planes, wherein at least two non-parallel optical sensors are used for each trajectory dimension of interest that differs from the primary direction of motion of the projectile and one additional optical sensor may be used for independent measurement of velocity attenuation.
Other fiber-optic based optical systems include ITT's Photonic Hit Indicator (PHI). The PHI is a fiber-optic grid that is designed to provide unique impact location indications for different flight test targets.
While these hit-point sensor systems accomplish their intended purpose of detecting or locating energetic impacts on a surface of interest, they are incapable of detecting multiple near simultaneous hit-points. Another feature of these systems, when used in high-velocity impact and explosives testing, is that the data must be retrieved and stored or transmitted in a very short time period. The particular amount of data to be stored, or transmitted, depends on the technique but is limited by the speed of preprocessing needed to reduce more complex raw data and the bandwidth of the data recording or telemetry system in use. It is therefore desirable to minimize the amount of data collected, processed, and transmitted to support determining the location of multiple energetic penetrations of a surface or volume and the subsequent progression of that penetration and damage in time.
The present invention is aimed at providing a sensor capable of locating multiple energetic penetrations of a surface or volume and recording the progression of that penetration and/or subsequent damage in time. It also is very data efficient and requires only a minimum of data throughput to provide these features, and therefore inherently provides higher speed recording of the events over that of currently available systems.